Electric-hydraulic pusher mechanism for heat treatment furnaces with safety stop control



Feb 1955 w. R. GILBERT 2,701,446

ELECTRIC-HYDRAULIC PUSHER' MECHANISM FOR HEAT I TREATMENT FURNACES WITHSAFETY STOP CONTROL Filed Jan. 10. 1952 4 Sheets-Sheet 1 IN V EN TOR.

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ELECTRIC-HYDRAULIC PUSHER MECHANISM FOR HEAT TREATMENT FURNACES WITHSAFETY STOP CONTROL Filed Jan. 10. 1952 4 Sheets-Sheet 2 FIG. 2

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ELECTRIC-HYDRAULIC PUSHER MECHANISM FOR HEAT TREATMENT FURNACES WITHSAFETY STOP CONTROL Filed Jan. 10. 1952 4 Sheets-Sheet 5- /4 /7 2/ /Z Z0MMM gm mnnuuuuni;

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ELECTRIC-HYDRAULIC PUSHER MECHANISM FOR HEAT TREATMENT FURNACES WITHSAFETY STOP CONTROL Filed Jan. 10, 1952 4 Sheets-Sheet 4 IINVENTOR. BY PW ATTORNEY United States Patent ELECTRIC-HYDRAULIC PUSHER MECHANISM FORHEAT TREATMENT FURNACES WITH SAFETY STOP CONTROL Wesley R. Gilbert,Cranston, R. I., assignor to C. I. Hayes, Inc., a corporation of RhodeIsland Application January 10, 1952, Serial No. 265,883

3 Claims. (Cl. 60-52) The present invention relates to the heattreatment art, and has particular reference to a novel construction fora pusher mechanism for a heating furnace.

The principal object of the invention is to provide a hydraulic pushermechanism which has a slow forward linear motion and a quick returnmotion.

Another object of the invention is to provide a hydraulic pushermechanism operated by a hydraulic system having means for controllingfluid flow to provide a slow forward movement.

A further object of the invention is to provide a hydraulic pushermechanism of the reciprocating type with drive operated electricalcontrols.

Another object of the invention is to provide a hydraulic pushermechanism with safety means for automatically stopping forward linearmotion when jamming occurs.

An additional object of the invention is to provide a hydraulic pushermechanism having alternative automatic or manual drive controls.

A further object is to provide a hydraulic pusher mechanism with ahydraulic flow circuit of large capacity and an adjustable back pressurecontrol.

It has been found desirable to provide a heat treatment furnace with ahydraulic pusher mechanism which advances work very slowly into theheating furnace. To this end, I have devised a novel hydraulic systemwhereby fluid under high pressure is pumped into the head end of a largepusher motor against regulated back pressure to provide a very slowforward linear motion of the pusher piston rod, and then into the rodend to produce a rapid return of the pusher piston rod, the hydraulicflow being controlled by a hydraulic solenoid valve. The solenoid valveis shifted by drive operated electric controls to change the directionof fluid flow to the pusher cylinder so as to selectively provide in tand out-strokes of the piston, a safety device being associated with thepiston rod whereby any jam or obstruction to forward motion of thepusher mechanism automatically stops the movement. The electricalcircuit which controls operation of the solenoid valve includes a relaysystem to automatically time each cycle of the pusher operation, thesystem having limit switches and a cycle timer which is manuallyregulated.

With the above and other objects and advantageous features in view, theinvention consists of a novel arrangement of parts more fully disclosedin the detailed description following, in conjunction with theaccompanying drawings, and more specifically defined in the claimsappended thereto.

In the drawings,

Fig. 1 is a side View of the front of the furnace showing the novelhydraulic pusher mechanism, parts being in section;

Fig. la is an enlarged detail of the pusher mechanism thrust device andits associated parts;

Fig. 2 is a view, partly broken away, of the front of the furnace;

Fig. 3 is an enlarged view of the hydraulic pusher mechanism and thrustdevice, the thrust slide being broken away;

Fig. 7 is a schematic view of the electrical control circuit showing therelay system; and

Fig. 8 is a schematic view of the hydraulic system.

The hydraulic pusher mechanism The pusher mechanism 10 is illustrated inFigs. 1, 1a, 2 and 3, and includes a cylinder 11 mounted on an elevatedsupport 12, and having a reciprocable piston 13 provided with a pistonrod 14, the parts being aligned with the inlet 15 of the heat treatmentfurnace 16. The outer end 17 of the piston rod is threaded to receivethe back plate 18 of a thrust device 19, the back plate being locked inplace by a lock nut 20 and washer 21.

The thrust device 19 includes a front plate 22, see Fig. 5, and a slidebase 23 which is slidably positioned over a work receiving table 24mounted on the support 12. The front plate 22 is secured to two similarspaced support rods 25 which are slidably received in bearing openings26 in the back plate 18, compression springs 27 encircling the rods 25between the back and front plates to exert an adjustable resilientthrust on the front plate as the back plate is advanced by the forwardlymoving piston rod. Each support rod 25 has a guide shell 28, see Fig. 5,which is secured to the back of the back plate, and the rear end 29 ofeach rod is threaded,

. for mounting an adjustable safety device as hereinafter described.

The hydraulic system The hydraulic system for reciprocating the pistonand piston rod and the thrust device is diagrammatically illustrated inFig. 8. It includes a tank 30, a pump 31 connected to the tank by aconduit 32 having a shutoff valve 33, and a control valve 34 which isconnected to the pump by conduits 35, 36 and to the tank 30 by a conduit37 having a relief pressure control valve 38. The control valve 34 isconnected to the head end of the cylinder 11 by a conduit 39, and to therod end of the cylinder 11 by a conduit 40, a check valve 41, and aconduit 42.

A by-pass conduit 43 connects the conduits 42 and 40, and includes anadjustable flow metering valve 44 as shown in Patent No. 2,051,052; adrain conduit 45 con nected to the flow metering valve and a return flowconduit 46 connected to the head end portion of the control valveconnected to the conduit 37.

The control valve 34 is shifted by an inflow solenoid 34a and an outflowsolenoid 34b, to alternatively supply pressure fluid to the head end ofthe cylinder at a pressure in accordance with the setting of thepressure control relief valve 38 While exhausting fluid from the rod endof the cylinder through the flow metering valve 44, or supply pressurefluid through the check valve 41 to the rod end while exhausting fluidfrom the head end through the conduit 46. The flow meter 44 is manuallyset to establish a desired back pressure in the rod end while the pistonis moving forwardly, whereby a very slow movement of the piston and thethrust device can be obtained. A shift of the control valve to neutralposition by a break in the solenoid operating circuit cuts off thepressure fluid to hold the piston stationary.

The electrical circuit for the control valve The electrical contacts forcontrolling reciprocation of the piston are illustrated in Fig. 6, thecomplete electric circuit being schematically illustrated in Fig. 7 andincludes a primary circuit A, a secondary circuit B and a transformer C.The primary circuit A has push button station selector switches a, agreen pilot light b, a resistor c for operating the green pilot light b,a red pilot light (I, a resistor e for operating the red pilot light 1d, relays f, four-Way solenoid valves g, a timer h, a limit Fig. 4 is atop plan view of the thrust device and its 1 1 switch i, a timersolenoid operated clutch j, an hydraulic pump motor starter k, andoverload switches l. The secondary circuit B has relays m1 through mix,micro switches n1 through us, a bell 0 and a timer load contact p. Theback plate 18 of the thrust device 19 is provided with two rearwardlyextending parallel rods 47, 48 which are slidably mounted in a switchsupport 49 and engage fixed brush contacts, to eliminate wiringconnection difficulties, the switch support including a front panel 50and a rear panel 51 and being secured to the support 12 intermediate thecylinder ends as shown in Fig. 1.

The rear panel 51 has two travel limit micro-switches 52, 53 securedthereto, the switch 52 being set to be contacted by an arm 54 adjustablylocked to the rod 48 at a point slightly before the desired thrustdevice travel and to provide for future delay in order to allow a timerto reset on instigation of a stroke, and the switch 53 being contactedby the arm 54 at the limit of the stroke. The completion of the circuitby contact of the arm 54 with micro-switch 53 at the outer limit of thereturn stroke operates a relay to shift the outflow solenoid into aneutral position and start a timer which will initiate another stroke atcompletion of the electrically timed cycle.

A third micro-switch S is secured to the front panel 5%, to be contactedby an arm 56 adjustably set on the rod 47 when the piston rod and thethrust device reach. the desired stroke limit. The completion of thecircuit by contact of the arm 56 with the micro-switch 55 operates therelay to shift the inflow solenoid and thus initiate the return stroke.

In addition, the electric circuit may be manually operated by a pushbutton 57 to stop the stroke movement at any point, and other pushbuttons 58, and 59 are provided to reverse, and begin forward movementas desired. Referring to the schematic illustration of the drive controlcircuit, as shown in Fig. 7, the layout comprising equipment ofconventional type, the operation is as follows: Before the power isturned on, the drive is in the extreme out-stroke position, theoutstroke limit switches I22 and 113 are in operated position (oppositefrom normal position shown), and the head safety switches :14 and us arein operative position. When power is turned on by closing selectorswitch a, the green pilot light b lights, the timer motor h runs, thetimer clutch solenoid j is energized, engaging the clutch and startingthe cycle, the motor starter operating coil k is energized, thetransformer C is energized, pushing head thrust overload relay ft isenergized, closing contacts mg in in-stroke relay 1", circuit.

When timer h times out, the timer load contacts 2 close completing acircuit through 57, in and p to ms.

T he thrust device safety control The thrust device safety control isillustrated in Fig. 5. The threaded rear ends 29 of each thrust devicesupport rod adjustably support micro-switch contact angles 61 which arelocked in position by lock nuts 62., 63. The angles 61 are set so thatspring pressure of the compression springs 27 press the front thrustplate forwardly to contact the forwardly projecting portions 64 of theangles 61 with micro-switches 65 mounted on the back plate l8; when anexcessive thrust pressure develops on the front thrust plate, thesupport rods are thrust back to break the micro-switch contact,Whereupon the circuit is broken and the control valve shifts to neutralposition to stop the forward movement and remain stopped until manuallystarted.

The operation of the hydraulic pusher mechanism is now clear. Theselector switch located on push button station No. 1 is closed to startautomatic drive operation. The green light signals that the drive is inop eration.

The motor driven hydraulic pump forces fluid from the fluid supply tankthrough the piping system under an operating pressure, preferably set at75 lbs. per sq. in., to the hydraulic solenoid valve which has beenenergized and shifted to permit fluid flow to the pusher cylinder forthe in-stroke movement of the piston and its piston rod. Upon completionof the in-stroke movement, the in-stroke limit switch is actuated andthe solenoid valve is shifted. The fluid now flows through the solenoidvalve directly to the rod end of the pusher cylinder for the out-strokemovement, which is stopped at completion by operation of the secondlimit switch, thus completing the hydraulic cycle and initiating a newcycle as described above, upon completion of the electrically timedcycle.

Stop push button station No. 1 may be manually operated at any time tostop the stroke and hold the pusher rod at rest. The push buttons atstation No. 7. are for emergency Stop, Reverse, and Forward. The Stopbutton will stop the stroke and the stroke may be restarted in eitherdirection by operation ofthe respective Forward or Reverse button. TheForward or Reverse buttons may be operated at any time while a stroke isin progress to change its direction, without first stopping the strokeby an operation of the Stop button.

The thrust overload device which is part of the pushing mechanism at theend of the hydraulic piston rod, is arranged so that the pushing thrustis delivered to the work trays through the intermediate compressionsprings, the springs being adjusted to equalize the thrust and toprovide a total thrust not exceeding one and onehalf times the thrustrequired to move the load. The open limit switches are mounted on theback thrust plate so that the spring pressure normally holds theircontacts closed; when the thrust pressure exceeds that for which thethrust adjustment is made, one or both switches will open to stop thedrive, which remains stopped until the overload or jam is relieved andresumption of the movement is started manually. The safety device isnecessary because a thrust of 1500 lbs. or more such as is needed for atypical heat treatment furnace for special steels will result fromoperation of a pusher mechanism with a six-inch piston, and will damagethe furnace and the work should a jam occur, as the normal thrustrequired to push a full line of sixinch work trays does not exceed 20lbs. This 1500 lbs. of thrust is the result of the lbs. per sq. in.requirement of the metering valve to obtain a metering at the very slowmotion of one-half inch per minute required for the operation. In orderto get the mini mum volume of flow which is meterable by the meteringvalve at this slow speed, it is necessary to use the large size cylinderwith six-inch piston.

The hydraulic system which reciprocates the piston and piston rod of thehydraulic cylinder is controlled by the regulating valve, which iselectrically shifted LO make the necessary fluid line connections forthe in and out strokes of the pusher piston. The control valve comprisesan in-stroke solenoid and an out-stroke solenoid; when neither solenoidis energized, the control valve is spring centered, all flow ports areclosed, and there is no motion of the pusher pump.

The motor driven hydraulic pump circulates fluid through the pressurerelief valve and the fluid supply tank through flow conduits 35 and 32,as shown in Fig. 8. When the in-stroke solenoid is energized, thecontrol valve shifts to connect the pump to the head end of the cylinderthrough conduit lines 35, 36 and 39, and to connect the rod end of thecylinder to the tank through conduit line 42, flow metering valve 4-4and line 40. The flow of fluid is from the tank to the pump, to thecontrol valve and pressure relief valve through lines 32 and 35. Therelief valve will not open until the fluid pressure in line 35 reachesthe pressure for which the relief valve is set, and thereafter passesexcess fluid back to the tank through line 37 while maintaining the setpressure in line 35, the relief valve being preferably set to open at 75lbs. per sq. in. The flow of fluid from the tank to the pump, to thecontrol valve and to the head end of the hydraulic cylinder through line39 maintains a fluid pressure on the head end corresponding to therelief valve setting, thus fluid pressure being transmitted through thepiston to the rod end of the cylinder, and through line 42 to themetering valve, the check valve being closed, the metering valve beingadjusted to permit a regulated escape of fluid through line 43, throughthe control valve and line 46 back to the tank, at a rate that providesa back pressure which results in the desired slew forward motion of thepiston.

When the out-stroke solenoid is energized, the control valve shifts toconnect the pump to the rod end of the cylinder through lines 35, it?and 42, see Fig. 8, and the head end of the cylinder to the tank throughlines 39 and 46. At this stage of the operation there is no backpressure restricting the movement of the piston, and the relief valve isinoperative as the pressure in line 35 builds up only to that requiredto move the piston and the fluid through the system. The flow ofpressure fluid is from the tank through the pump, through the controlvalve, through the check valve, and to the rod end of the cylinder, thefluid being forced from the head end of the cylinder through the controlvalve to the tank through lines 39 and 46. There is thus a rapid returnmovement of the piston, piston rod and thrust head.

It is clear that the novel hydraulic pusher mechanism described providesa veryvsiow advancement of work into and through the furnace to complywith prescribed heating requirements. Moreover, the novel constructionis time saving due to rapid return motion of the thrust head to permitfeeding of additional work, which advances the preceding work throughthe furnace, thus keeping a steady flow of work through the heatingfurnace at the prescribed rate of feed necessary to accomplish the heattreatment operation.

Although I have described a specific constructional embodiment of myinvention, it is clear that changes in the size, shape and arrangementof the parts may be made to suit different requirements, withoutdeparting from the spirit and the scope of the invention as defined inthe appended claims.

I claim:

1. A hydraulic pusher mechanism for a heating furnace, comprising apusher cylinder having a piston and including travel limitmicro-switches, said piston having a piston rod, said piston rod havinga back plate secured to its forward end, a micro-switch device mountedon said back plate, a pusher plate positioned forward of said backplate, means securing said back plate to said pusher plate includingspring means urging said plates away from each other, contact elementson said securing means normally in contact with the back platemicro-switch device when the forward pusher plate is in its maximumspaced position away from the back plate and out of contact with thesaid micro-switch device when the forward pusher plate compresses thespring means in response to excessive pressure on the pusher plate, ahydraulic system including a fluid tank, a conduit circuit leading fromsaid tank to the ends of the cylinder, a pump in said circuit wherebyliquid is forced through the circuit, a pressure control valve,intermediate the pump and the fluid tank, whereby pressure flow throughthe control valve is maintained, a flow metering valve intermediate theexhaust end of the pusher cylinder and the fluid tank, whereby the rateof flow from the exhaust end to the tank is controlled, a check valveintermediate the exhaust end of the pusher cylinder and the fluid tank,whereby the fluid flow is forced through the metering valve, and anelectrical circuit, said conduit circuit. including a solenoid controlvalve for selectively controlling flow of liquid to the ends of thecylinder, said electrical circuit connecting the micro-switches on saidpusher cylinder to the solenoid control valve for shifting the solenoidsto selectively control the supply of liquid through the solenoid valveand the ends of the cylinder and the microswitch device on said backplate to the solenoid valve for shifting the solenoids to neutralposition to stop flow of liquid to the cylinder.

2. A hydraulic pusher mechanism for a heating furnace, comprising apusher cylinder having a piston and including travel limitmicro-switches, said piston having a piston rod, said piston rod havinga back plate secured to its forward end, micro-switches and spaced guidesleeves on said back plate, rods slidably received within said guidesleeves, a pusher plate positioned forward of said back plate andsecured to the rods, spring means on said rods positioned intermediatesaid back plate and said forward pusher plate and resiliently urgingsaid plates away from each other, contact elements on said rods normallyin contact with the back plate micro-switches when the forward pusherplate is in its maximum spaced position away from the back plate and outof contact with the said micro-switches when the forward pusher platecompresses the spring means in response to excessive pressure on thepusher plate, a hydraulic system including a fluid tank, a conduitcircuit leading from said tank to the ends of the cylinder, a pump insaid circuit whereby liquid is forced through the circuit, a pressurecontrol valve, intermediate the pump and the fluid tank, wherebypressure flow through the control vale is maintained, a flow meteringvalve intermediate the exhaust end of the pusher cylinder and the fluidtank, whereby the rate of flow from the exhaust end to the tank iscontrolled, a check valve intermediate the exhaust end of the pushercylinder and the fluid tank, whereby the fluid flow is forced throughthe metering valve, and an electrical circuit, said conduit circuitincluding a solenoid control valve for selectively controlling flow ofliquid to the ends of the cylinder, said electrical circuit connectingthe microswitches on said pusher cylinder to the solenoid control valvefor shifting the solenoids to selectively control the supply .of liquidthrough the solenoid valve and the ends of the cylinder and themicro-switches on said back plate to the solenoid valve for shifting thesolenoids to neutral position to stop flow of liquid to the cylinder.

3. An overload device for a hydraulic pusher mechanism consisting of aback plate adapted to be secured to the forward end of a piston rod andhaving a microswitch device 'thereon, a pusher plate positioned forwardof said back plate, means securing said pusher plate to said back plateand having a spring element urging said plates away from each other,said spring element being compressed when excessive pressure is exertedon the pusher plate, a contact on said securing means normally incontact with the micro-switch device when the pusher plate is in itsmaximum spaced position away from the back plate and out of contact withthe micro-switch device when the pusher plate moves towards the backplate and compresses the spring element.

References Cited in the file of this patent UNITED STATES PATENTS1,877,161 Conklin Sept. 13, 1932 2,130,764 Conklin Sept. 20, 19382,327,920 Moohl Aug. 24, 1943 2,367,241 Stacy Jan. 16, 1945 2,424,138Barr July 15, 1947 2,529,777 McInnis Nov. 14, 1950 2,603,950 MatheysJuly 22, 1952 2,605,751 Perry et al. Aug. 5, 1952 2,612,951 PalmleafOct. 7, 1952

